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                                                                   Exhibit 10.13

                            MASTER SECURITY AGREEMENT
                                   NO. 4081064
                     Dated as of JULY 30, 2004 ("AGREEMENT")

      THIS AGREEMENT (this "Agreement") is between OXFORD FINANCE CORPORATION
(together with its successors and assigns, if any, "SECURED PARTY") and PTC
Therapeutics, Inc. ("DEBTOR"). Secured Party has an office at 133 N. Fairfax
Street, Alexandria, VA 22314. Debtor is a corporation organized and existing
under the laws of the state of Delaware. Debtor's mailing address and chief
place of business is 100 Corporate Court, South Plainfield, NJ 07080.

1.    CREATION OF SECURITY INTEREST.

      Debtor grants to Secured Party, its successors and assigns, a security
interest in and against all property listed on any collateral schedule now or in
the future annexed to or made a part of this Agreement ("COLLATERAL SCHEDULE"),
and in and against all additions, attachments, accessories and accessions to
such property, all substitutions, replacements or exchanges therefore, and all
insurance and/or other proceeds thereof (all such property is individually and
collectively called the "COLLATERAL"). This security interest is given to secure
the payment and performance of certain Promissory Notes from time to time
identified on any Collateral Schedule (collectively "NOTES" and each a "NOTE"),
the "Debt Documents" (as defined below), and any renewals, extensions and
modifications of such debts, obligations and liabilities (such Notes, debts,
obligations and liabilities are called the "INDEBTEDNESS"). Debtor acknowledges
that, notwithstanding that the Note(s) may be paid in full, this Security
Agreement shall continue to secure the payment and performance of any remaining
Indebtedness of Debtor to Secured Party, now existing or arising in the future,
and that Secured Party shall be under no obligation to release the Collateral
unless and until all Indebtedness of Debtor to Secured Party has been paid and
satisfied; provided, however, Secured Party, in its sole and exclusive
discretion, may elect to release some of the Collateral without prejudice to
Secured Party's security interest in the remaining Collateral. Unless otherwise
provided by applicable law, notwithstanding anything to the contrary contained
in this Agreement, to the extent that Secured Party asserts a purchase money
security interest in any items of Collateral ("PMSI COLLATERAL"): (i) the PMSI
Collateral shall secure only that portion of the Indebtedness which has been
advanced by Secured Party to enable Debtor to purchase, or acquire rights in or
the use of such PMSI Collateral (the "PMSI INDEBTEDNESS"), and (ii) no other
Collateral shall secure the PMSI Indebtedness.

2.    REPRESENTATIONS, WARRANTIES AND COVENANTS OF DEBTOR.

      Debtor represents, warrants and covenants as of the date of this Agreement
and as of the date of each Collateral Schedule that:

      (a)   Debtor's exact legal name is as set forth in the preamble of this
            Agreement (or, upon any change thereto, Debtor will notify Secured
            Party in accordance with the terms of this Agreement) and Debtor is,
            and will remain, duly organized, existing and in good standing under
            the laws of the State set forth in the preamble of this Agreement,
            has its chief executive offices at the location specified in the
            preamble (or, upon any change thereto, Debtor will notify Secured
            Party in accordance with the terms of this Agreement), and is, and
            will remain, duly qualified and licensed in every jurisdiction
            wherever necessary to carry on its business and operations;

      (b)   Debtor has adequate power and capacity to enter into, and to perform
            its obligations under this Agreement, each Note and any other
            documents evidencing, or given in connection with, any of the
            Indebtedness (all of the foregoing are called the "DEBT DOCUMENTS");

      (c)   This Agreement and the other Debt Documents have been duly
            authorized, executed and delivered by Debtor and constitute legal,
            valid and binding agreements enforceable in accordance with their
            terms, except to the extent that the enforcement of remedies may be
            limited under applicable bankruptcy and insolvency laws;

      (d)   No approval, consent or withholding of objections is required from
            any governmental authority or instrumentality with respect to the
            entry into, or performance by Debtor of any of the Debt Documents,
            except any already obtained;

      (e)   The entry into, and performance by, Debtor of the Debt Documents
            will not (i) violate any of the organizational documents of Debtor
            or any judgment, order, law or regulation applicable to Debtor, or
            (ii) result in any breach of or constitute a default under any
            contract to which Debtor is a party, or result in the creation of
            any lien, claim or encumbrance on any of Debtor's property (except
            for liens in favor of Secured Party) pursuant to any indenture,
            mortgage, deed of trust, bank loan, credit agreement, or other
            agreement or instrument to which Debtor is a party;

      (f)   Except as otherwise disclosed to Secured Party, there are no suits
            or proceedings pending in court or before any commission, board or
            other administrative agency against or affecting Debtor which could,
            in the aggregate, have a material adverse effect on Debtor, its
            business or operations, or its ability to perform its obligations
            under the Debt Documents, nor does Debtor have reason to believe
            that any such suits or proceedings are threatened;

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      (g)   All financial statements delivered to Secured Party in connection
            with the Indebtedness have been prepared in accordance with
            generally accepted accounting principles, and since the date of the
            most recent financial statement, there has been no material adverse
            change in Debtors financial condition;

      (h)   The Collateral is not, and will not be, used by Debtor for personal,
            family or household purposes;

      (i)   The Collateral is, and will remain, in good condition and repair and
            Debtor will not be negligent in its care and use;

      (j)   All of the tangible Collateral is located at the locations set forth
            on each Collateral Schedule. Debtor shall give the Secured Party 30
            days prior written notice of any relocation of any Collateral (other
            than between such locations);

      (k)   Debtor is, and will remain, the sole and lawful owner, and in
            possession of, the Collateral, and has the sole right and lawful
            authority to grant the security interest described in this
            Agreement;

      (l)   The Collateral is, and will remain, free and clear of all liens,
            claims and encumbrances of any kind whatsoever, except for (i) liens
            in favor of Secured Party, (ii) liens for taxes not yet due or for
            taxes being contested in good faith and which do not involve, in the
            reasonable judgment of Secured Party, any risk of the sale,
            forfeiture or loss of any of the Collateral, and (iii) inchoate
            material men's, mechanic's, repairmen's and similar liens arising by
            operation of law in the normal course of business for amounts which
            are not delinquent (all of such liens are called "PERMITTED LIENS");

      (m)   All federal, state and local tax returns required to be filed by
            Debtor have been filed with the appropriate governmental agencies
            and all taxes due and payable by Debtor have been timely paid.
            Debtor will pay when due all taxes, assessments and other
            liabilities except as contested in good faith and by appropriate
            proceedings and for which adequate reserves have been established;
            provided, however, the omission to file and/or pay any related fine
            in connection with any employee benefit plan for the calendar years
            ending in 2002 and 2003 shall not be deemed a breach of this
            Subsection 2(m);

      (n)   No event or condition exists under any material agreement,
            instrument or document to which Debtor is a party or may be subject,
            or by which Debtor or any of its properties are bound, which
            constitutes a default or an event of default thereunder;

      (o)   All reports, certificates, schedules, notices and financial
            information submitted by Debtor to the Secured Party pursuant to
            this Agreement shall be certified as true and correct by the
            president or chief financial officer of Debtor; provided, however,
            if and to the extent that Secured Party accepts reports,
            certificates, schedules, notices and financial information without
            the required certification or fails to provide an objection to the
            omission to provide the required certification, the omission to
            certify shall not be deemed a breach of this Subsection 2(o);

      (p)   Debtor shall give the Secured Party prompt written notice of any
            event, occurrence or other matter which has resulted or may result
            in a material adverse change in its financial condition, business
            operations, prospects, product development, technology, or business
            or contractual relations with third parties of Debtor which would
            impair the ability of Debtor to perform its obligations hereunderor
            under any of the other material financing agreements to which it is
            a party or of Secured Party to enforce the Indebtedness or realize
            upon the Collateral; and

      (q)   Debtor has previously delivered to the Secured Party a certificate
            signed by the Debtor and entitled "Perfection Certificate" (the
            "PERFECTION CERTIFICATE"). The Debtor represents and warrants to the
            Secured Party as follows: (a) the Debtor's exact legal name is that
            indicated on the Perfection Certificate and on the signature page
            hereof, (b) the Debtor is an organization of the type, and is
            organized in the jurisdiction set forth in the Perfection
            Certificate, (c) the Perfection Certificate accurately sets forth
            the Debtor's organizational identification number or accurately
            states that the Debtor has none, (d) the Perfection Certificate
            accurately sets forth the Debtor's place of business or, if more
            than one, its chief executive office, as well as the Debtor's
            mailing address, if different, (e) all other information set forth
            on the Perfection Certificate pertaining to the Debtor is accurate
            and complete, and (f) that there has been no change in any
            information provided in the Perfection Certificate since the date on
            which it was executed by the Debtor other than any change of which
            Debtor has notified Secured Party in accordance with the terms of
            this Agreement.

3.    COLLATERAL.

      (a)   Until the declaration of any default, Debtor shall remain in
            possession of the Collateral; except that Secured Party shall have
            the right to possess (i) any chattel paper or instrument that
            constitutes a part of the Collateral, and (ii) any other Collateral
            in which Secured Party's security interest may be perfected only by
            possession. Secured Party may inspect any of the Collateral during
            normal business hours after giving Debtor reasonable prior notice.

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      (b)   Debtor shall (i) use the Collateral only in its trade or business,
            (ii) maintain all of the Collateral in good operating order and
            repair, normal wear and tear excepted, (iii) use and maintain the
            Collateral only in compliance with manufacturers recommendations and
            all applicable laws, and (iv) keep all of the Collateral free and
            clear of all liens, claims and encumbrances (except for Permitted
            Liens).

      (c)   Secured Party does not authorize and Debtor agrees it shall not (i)
            part with possession of any of the Collateral (except to Secured
            Party or for maintenance and repair), (ii) remove any of the
            Collateral from the continental United States, or (iii) sell, rent,
            lease, mortgage, license, grant a security interest in or otherwise
            transfer or encumber (except for Permitted Liens) any of the
            Collateral.

      (d)   Debtor shall pay promptly when due all taxes, license fees,
            assessments and public and private charges levied or assessed on any
            of the Collateral, on its use, or on this Agreement or any of the
            other Debt Documents. At its option, Secured Party may discharge
            taxes, liens, security interests or other encumbrances at any time
            levied or placed on the Collateral and may pay for the maintenance,
            insurance and preservation of the Collateral and effect compliance
            with the terms of this Agreement or any of the other Debt Documents,
            provided that, Secured Party shall not take any of such actions
            unless and until Debtor has failed to do so in a timely manner,
            Secured Party has delivered to Debtor written notice of any such
            failure, and Debtor has not cured such failure within ten days after
            receipt of such written notice. Debtor agrees to reimburse Secured
            Party, on demand, all costs and expenses incurred by Secured Party
            in connection with such payment or performance and agrees that such
            reimbursement obligation shall constitute Indebtedness.

      (e)   Debtor shall, at all times, keep accurate and complete records of
            the Collateral, and Secured Party shall have the right to inspect
            and make copies of all of Debtor's books and records relating to the
            Collateral during normal business hours, after giving Debtor
            reasonable prior notice.

      (f)   Debtor agrees and acknowledges that any third person who may at any
            time possess all or any portion of the Collateral shall be deemed to
            hold, and shall hold, the Collateral as the agent of, and as pledge
            holder for, Secured Party. Secured Party may at any time give notice
            to any third person described in the preceding sentence that such
            third person is holding the Collateral as the agent of, and as
            pledge holder for, the Secured Party.

4.    INSURANCE.

      (a)   Debtor shall at all times bear the entire risk of any loss, theft,
            damage to, or destruction of, any of the Collateral from any cause
            whatsoever, subject to the limitations set forth in Section 6(c).

      (b)   Debtor agrees to keep the Collateral insured against loss or damage
            by fire and extended coverage perils, theft, burglary, and for any
            or all Collateral, which are vehicles, for risk of loss by
            collision, and if requested by Secured Party, against such other
            risks as Secured Party may reasonably require. The insurance
            coverage shall be in an amount no less than the full replacement
            value of the Collateral, and deductible amounts, insurers and
            policies shall be acceptable to Secured Party. Debtor shall deliver
            to Secured Party policies or certificates of insurance evidencing
            such coverage. Each such policy or certificate shall name Secured
            Party as a loss payee, shall not be subject to co-insurance, and
            shall provide that if coverage is canceled or lowered, the insurer
            shall give thirty (30) days prior written notice to Secured Party.
            Debtor appoints Secured Party as its attorney-in-fact to make proof
            of loss, claim for insurance and adjustments with insurers, and to
            receive payment of and execute or endorse all documents, checks or
            drafts in connection with insurance payments. Secured Party shall
            not act as Debtor's attorney-in-fact unless Debtor is in default
            under the Debt Documents. Proceeds of insurance shall be applied, at
            the option of Secured Party, to repair or replace the Collateral or
            to reduce any of the Indebtedness.

5.    REPORTS.

      (a)   Debtor shall promptly notify Secured Party of (i) any change in the
            name of Debtor, (ii) any change in the state of its incorporation or
            registration, (iii) any relocation of its chief executive offices,
            (iv) any of the Collateral being lost, stolen, missing, destroyed,
            materially damaged or worn out, or (v) any lien, claim or
            encumbrance other than Permitted Liens attaching to or being made
            against any of the Collateral.

      (b)   Debtor will deliver to Secured Party within one hundred twenty (120)
            days of the close of each fiscal year of Debtor, a copy of the
            annual audit report of Debtor, including a balance sheet, income
            statement, statement of shareholders' equity and statement of cash
            flows, each prepared in accordance with generally accepted
            accounting principles consistently applied, certified by a
            recognized firm of certified public accountants. Debtor will deliver
            to Secured Party copies of Debtor's balance sheet, income statement
            and statement of cash flows, each prepared by Debtor in accordance
            with generally accepted accounting principles consistently applied
            by Debtor and certified (subject to year-end audit adjustments) by
            Debtor's chief financial officer, within ninety (90) days after the
            close of each of the first three quarters of each fiscal year of
            Debtor. Debtor will deliver to Secured Party copies of all Forms
            10-K and 10-Q, if any, within 30 days after the dates on which they
            are filed with the Securities and Exchange Commission. Debtor will
            deliver to Secured Party copies of monthly bank account statements
            or other statements provided with respect to Debtor's cash
            management activities within forty-five (45) days after the close of
            each month.

      (c)   Secured Party promptly upon request of Secured Party, in form
            satisfactory to Secured Party, such other and additional information
            as Secured Party may reasonably request from time to time, provided
            that,

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            i.    Such additional information exists or could be created without
                  significant additional cost on the part of Debtor;

            ii.   If Debtor indicates such additional information is
                  confidential or proprietary, Secured Party will provide
                  written assurances of confidential treatment upon Debtor's
                  request, ensure limited access to such additional information,
                  and guarantee no improper use or transfer thereof; and

            iii.  Such additional information will not violate any law,
                  regulation or contractual or other obligation by which Debtor
                  is bound.

6.    FURTHER ASSURANCES.

      (a)   Debtor shall, upon request of Secured Party, furnish to Secured
            Party such further information, execute and deliver to Secured Party
            such documents and instruments (including, without limitation,
            Uniform Commercial Code financing statements) and shall do such
            other acts and things as Secured Party may at any time reasonably
            request to perfect or protect the security interest created by this
            Agreement or for the purpose of carrying out the intent of this
            Agreement. Without limiting the foregoing, Debtor shall cooperate
            and do all acts reasonably deemed necessary or advisable by Secured
            Party to continue in Secured Party a perfected first security
            interest in the Collateral, and shall use its best efforts under the
            circumstances to obtain and furnish to Secured Party any
            subordinations, releases, landlord waivers, lessor waivers,
            mortgagee waivers, or control agreements, and similar documents as
            may be from time to time reasonably requested by, and in form and
            substance reasonably satisfactory to, Secured Party.

      (b)   Debtor shall use its best efforts under the circumstances to perform
            any and all acts requested by the Secured Party to establish,
            maintain and continue the Secured Party's security interest and
            liens in the Collateral, including but not limited to, executing or
            authenticating financing statements and such other instruments and
            documents when and as reasonably requested by the Secured Party.
            Debtor hereby authorizes Secured Party through any of Secured
            Party's employees, agents or attorneys to file any and all financing
            statements, including, without limitation, any original filings,
            continuations, transfers or amendments thereof required to perfect
            Secured Party's security interest and liens in the Collateral under
            the UCC without authentication or execution by Debtor. Debtor hereby
            irrevocably authorizes the Secured Party at any time and from time
            to time to file in any filing office in any Uniform Commercial Code
            jurisdiction any initial financing statement(s) and amendments
            thereto that (a) indicate the Collateral (i) is subject to the
            Secured Party's security interest, regardless of whether any
            particular asset comprised in the Collateral falls within the scope
            of Article 9 of the Uniform Commercial Code of the State or such
            jurisdiction, or (ii) as being of an equal or lesser scope or with
            greater detail, and (b) provide any other information required by
            part 5 of Article 9 of the Uniform Commercial Code of the State or
            such other jurisdiction for the sufficiency or filing office
            acceptance of any financing statement or amendment, including (i)
            whether the Debtor is an organization, the type of organization and
            any organization identification number issued to the Debtor, and
            (ii) in the case of a financing statement filed as a fixture filing,
            a sufficient description of real property to which the Collateral
            relates. The Debtor agrees to furnish any such information to the
            Secured Party promptly upon the Secured Party's request.

      (c)   Debtor shall indemnify and defend the Secured Party, its successors
            and assigns, and their respective directors, officers and employees,
            from and against all claims, actions and suits (including, without
            limitation, related attorneys' fees) of any kind whatsoever arising,
            directly or indirectly, in connection with any of the Collateral,
            provided that, Debtor shall have no such obligation to indemnify or
            defend Secured Party or any such entities or persons from and
            against any such claims, actions or suits (including without
            limitation attorneys' fees) arising, directly or indirectly, in
            connection with any of the following:

            (i) Secured Party's or its agents' failure to comply with any
            applicable laws, rules or regulations in relation to its handling,
            use or transport of the Collateral;

            (ii) Secured Party's or its agents' failure to utilize properly
            trained or experienced personnel for the handling, use or transport
            of any materials or other items of Collateral which constitute or
            contain hazards or dangers known or identified to Secured Party as
            such; or

            (iii) Secured Party's or its agents' gross negligence or willful
            misconduct.

7.    DEFAULT AND REMEDIES.

      (a)   Debtor shall be in default under this Agreement and each of the
            other Debt Documents if:

            (i)   Debtor breaches its obligation to pay when due any installment
                  or other amount due or coming due under any of the Debt
                  Documents and fails to cure such breach within five (5) days
                  of when due;

            (ii)  Debtor, without the prior written consent of Secured Party,
                  attempts to or does sell, rent, lease, license, mortgage,
                  grant a security interest in, or otherwise transfer or
                  encumber (except for Permitted Liens) any of the Collateral;

            (iii) Debtor breaches any of its insurance obligations under Section
                  4;

            (iv)  Debtor breaches any of its other non-payment obligations under
                  any of the Debt Documents and fails to cure that breach within
                  thirty (30) days after written notice from Secured Party;

            (v)   Any material warranty, representation or statement made by
                  Debtor in any of the Debt Documentsor otherwise in connection
                  with any of the Indebtedness shall be false or misleading in
                  any material respect as of the date made;

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            (vi)  Any of the Collateral is subjected to attachment, execution,
                  levy, seizure or confiscation in any legal proceeding or
                  otherwise, or if any legal or administrative proceeding is
                  commenced against Debtor or any of the Collateral, which in
                  the good faithreasonable judgment of Secured Party subjects
                  any of the Collateral to a material risk of attachment,
                  execution, levy, seizure or confiscation and no bond is posted
                  or protective order obtained to negate such risk;

            (vii) Debtor breaches or is in default under any other agreement
                  between Debtor and Secured Party;

            (viii) Debtor or any guarantor or other obligor for any of the
                  Indebtedness (collectively "GUARANTOR") dissolves, terminates
                  its existence, becomes insolvent or ceases to do business as a
                  going concern;

            (ix)  With respect to any Debtor or any Guarantor who is a natural
                  person, Debtor or any such Guarantor dies or becomes
                  incompetent;

            (x)   A receiver is appointed for all or of any part of the property
                  of Debtor or any Guarantor, or Debtor or any Guarantor makes
                  any assignment for the benefit of creditors;

            (xi)  Debtor or any Guarantor files a petition under any bankruptcy,
                  insolvency or similar law, or any such petition is filed
                  against Debtor or any Guarantor and is not dismissed within
                  forty-five (45) days;

            (xii) Debtor's improper filing of an amendment or termination
                  statement relating to a filed financing statement describing
                  the Collateral.

            (xiii) Except with the Secured Party's prior written consent which
                  shall not be unreasonably withheld, conditioned or delayed,
                  Debtor shall merge with or consolidate into any other entity
                  or sell all or substantially all of its assets or in any
                  manner terminate its existence;

            (xiv) Except with the Secured Party's prior written consent which
                  shall not be unreasonably withheld, conditioned or delayed,
                  Debtor is a privately held corporation, more than 50% of
                  Debtor's voting capital stock, or effective control of
                  Debtor's voting capital stock, issued and outstanding from
                  time to time, is not retained by the holders of such stock on
                  the date the Agreement is executed;

            (xv)  Except with the Secured Party's prior written consent which
                  shall not be unreasonably withheld, conditioned or delayed,
                  Debtor is a publicly held corporation, there shall be a change
                  in the ownership of Debtor's stock such that Debtor is no
                  longer subject to the reporting requirements of the Securities
                  Exchange Act of 1934 or no longer has a class of equity
                  securities registered under Section 12 of the Securities Act
                  of 1933;

            (xvi) Debtor defaults under any other material financing arrangement
                  between Debtor and a third party; and

            (xvii) A change or event shall have occurred which would impair the
                  ability of Debtor to perform its material obligations
                  hereunder or of Secured Party to enforce the Indebtedness or
                  realize upon the Collateral;

      (b)   If Debtor is in default, the Secured Party, at its option, may
            declare any or all of the Indebtedness to be immediately due and
            payable, without demand or notice to Debtor or any Guarantor. The
            accelerated obligations and liabilities shall bear interest (both
            before and after any judgment) until paid in full at the lower of
            thirteen percent (13%) per annum or the maximum rate not prohibited
            by applicable law.

      (c)   Upon a default of this Agreement by Debtor or the occurrence of an
            event which would constitute a default, Secured Party shall have all
            of the rights and remedies of a Secured Party under the Uniform
            Commercial Code, and under any other applicable law. Without
            limiting the foregoing, Secured Party shall have the right in such
            circumstances to (i) notify any account debtor of Debtor or any
            obligor on any instrument which constitutes part of the Collateral
            to make payment to the Secured Party, (ii) with or without legal
            process, enter any premises where the Collateral may be and take
            possession of and remove the Collateral from the premises or store
            it on the premises, (iii) sell the Collateral at public or private
            sale, in whole or in part, and have the right to bid and purchase at
            said sale, or (iv) lease or otherwise dispose of all or part of the
            Collateral, applying proceeds from such disposition to the
            obligations then in default. Upon a default of this Agreement by
            Debtor or the occurrence of an event that would constitute a
            default, if requested by Secured Party, Debtor shall promptly
            assemble the Collateral and make it available to Secured Party at a
            place to be designated by Secured Party, which is reasonably
            convenient to both parties. Upon a default of this Agreement by
            Debtor or the occurrence of an event which would constitute a
            default, Secured Party may also render any or all of the Collateral
            unusable at the Debtor's premises and may dispose of such Collateral
            on such premises without liability for rent or costs. Any notice
            that Secured Party is required to give to Debtor under the Uniform
            Commercial Code of the time and place of any public sale or the time
            after which any private sale or other intended disposition of the
            Collateral is to be made shall be deemed to constitute reasonable
            notice if such notice is given to the last known address of Debtor
            at least five (5) days prior to such action. Upon a default of this
            Agreement by Debtor or the occurrence of an event of default and
            during the continuation of such default or event, Debtor hereby
            appoints Secured Party as Debtor's attorney-in-fact, with full
            authority in Debtor's place and stead and in Debtor's name or
            otherwise, from time to time in Secured Party's sole and arbitrary
            discretion, to take any action and to execute any instrument which
            Secured Party reasonably deems necessary or advisable to accomplish
            the purpose of this Agreement.

      (d)   Proceeds from any sale or lease or other disposition shall be
            applied: first, to all costs of repossession, storage, and
            disposition including without limitation attorneys', appraisers',
            and auctioneers' fees; second, to discharge the obligations then in
            default; third, to discharge any other Indebtedness of Debtor to
            Secured Party, whether as obligor, endorser, guarantor, surety or
            indemnitor; fourth, to expenses incurred in paying or settling liens
            and claims against the Collateral; and lastly, to Debtor, if there
            exists any surplus. Debtor shall remain fully liable for any
            deficiency.

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      (e)   Upon a default of this Agreement by Debtor or the occurrence of an
            event which with the passage of time or the giving of notice would
            constitute a default, Debtor agrees to pay all reasonable attorneys'
            fees and other costs incurred by Secured Party in connection with
            the enforcement, assertion, defense or preservation of Secured
            Party's rights and remedies under this Agreement, or if prohibited
            by law, such lesser sum as may be permitted. Debtor further agrees
            that such fees and costs shall constitute Indebtedness.

      (f)   Secured Party's rights and remedies under this Agreement or
            otherwise arising are cumulative and may be exercised singularly or
            concurrently. Neither the failure nor any delay on the part of the
            Secured Party to exercise any right, power or privilege under this
            Agreement shall operate as a waiver, nor shall any single or partial
            exercise of any right, power or privilege preclude any other or
            further exercise of that or any other right, power or privilege.
            SECURED PARTY SHALL NOT BE DEEMED TO HAVE WAIVED ANY OF ITS RIGHTS
            UNDER THIS AGREEMENT OR UNDER ANY OTHER AGREEMENT, INSTRUMENT OR
            PAPER SIGNED BY DEBTOR UNLESS SUCH WAIVER IS EXPRESSED IN WRITING
            AND SIGNED BY SECURED PARTY. A waiver on any one occasion shall not
            be construed as a bar to or waiver of any right or remedy on any
            future occasion.

      (g)   DEBTOR AND SECURED PARTY UNCONDITIONALLY WAIVE THEIR RIGHTS TO A
            JURY TRIAL OF ANY CLAIM OR CAUSE OF ACTION BASED UPON OR ARISING OUT
            OF THIS AGREEMENT, ANY OF THE OTHER DEBT DOCUMENTS, ANY OF THE
            INDEBTEDNESS SECURED HEREBY, ANY DEALINGS BETWEEN DEBTOR AND SECURED
            PARTY RELATING TO THE SUBJECT MATTER OF THIS TRANSACTION OR ANY
            RELATED TRANSACTIONS, AND/OR THE RELATIONSHIP THAT IS BEING
            ESTABLISHED BETWEEN DEBTOR AND SECURED PARTY. THE SCOPE OF THIS
            WAIVER IS INTENDED TO BE ALL ENCOMPASSING OF ANY AND ALL DISPUTES
            THAT MAY BE FILED IN ANY COURT. THIS WAIVER IS IRREVOCABLE. THIS
            WAIVER MAY NOT BE MODIFIED EITHER ORALLY OR IN WRITING. THE WAIVER
            ALSO SHALL APPLY TO ANY SUBSEQUENT AMENDMENTS, RENEWALS, SUPPLEMENTS
            OR MODIFICATIONS TO THIS AGREEMENT, ANY OTHER DEBT DOCUMENTS, OR TO
            ANY OTHER DOCUMENTS OR AGREEMENTS RELATING TO THIS TRANSACTION OR
            ANY RELATED TRANSACTION. THIS AGREEMENT MAY BE FILED AS A WRITTEN
            CONSENT TO A TRIAL BY THE COURT.

8.    MISCELLANEOUS.

            (a)   This Agreement, any Note and/or any of the other Debt
                  Documents may be assigned, in whole or in part, by Secured
                  Party without notice to Debtor, and Debtor agrees not to
                  assert against any such assignee, or assignee's assigns, any
                  set-off, recoupment claim or counterclaim which Debtor has or
                  may at any time have against Secured Party for any reason
                  whatsoever, except in any case of the defense of payment.
                  Debtor agrees that if Debtor receives written notice of an
                  assignment from Secured Party, Debtor will pay all amounts
                  payable under any assigned Debt Documents to such assignee or
                  as instructed by Secured Party. Debtor also agrees to confirm
                  in writing receipt of the notice of assignment as may be
                  reasonably requested by Secured Party or assignee.

            (b)   All notices to be given in connection with this Agreement
                  shall be in writing, shall be addressed to the parties at
                  their respective addresses set forth in this Agreement (unless
                  and until a different address may be specified in a written
                  notice to the other party), and, in the case of all such
                  notices to Debtor, a copy shall be sent by email to
                  legal@ptcbio.com, and shall be deemed given (i) on the date of
                  receipt if delivered in hand or by facsimile transmission,
                  (ii) on the next business day after being sent by express
                  mail, and (iii) on the fourth business day after being sent by
                  regular, registered or certified mail. As used herein, the
                  term "business day" shall mean and include any day other than
                  Saturdays, Sundays, or other days on which commercial banks in
                  New York, New York are required or authorized to be closed.

            (c)   Upon notice to Debtor, Secured Party may fill in all blanks in
                  any Collateral Schedule consistent with the agreement of the
                  parties. With the consent of Debtor, Secured Party may correct
                  patent errors and fill in all blanks in this Agreement
                  consistent with the terms hereof, provided that, consistent
                  with the agreement of the parties, Secured Party may fill in
                  the date in any Note or this Agreement without further notice
                  to or consent of Debtor.

            (d)   Time is of the essence of this Agreement. This Agreement shall
                  be binding, jointly and severally, upon all parties described
                  as the "Debtor" and their respective heirs, executors,
                  representatives, successors and assigns, and shall inure to
                  the benefit of Secured Party, its successors and assigns.

            (e)   This Agreement and its Collateral Schedules constitute the
                  entire agreement between the parties with respect to the
                  subject matter of this Agreement and supersede all prior
                  understandings (whether written, verbal or implied) with
                  respect to such subject matter. THIS AGREEMENT AND ITS
                  COLLATERAL SCHEDULES SHALL NOT BE CHANGED OR TERMINATED ORALLY
                  OR BY COURSE OF CONDUCT, BUT ONLY BY A WRITING SIGNED BY BOTH
                  PARTIES. Section headings contained in this Agreement have
                  been included for convenience only, and shall not affect the
                  construction or interpretation of this Agreement.

            (f)   This Agreement shall continue in full force and effect until
                  all of the Indebtedness has been indefeasibly paid in full to
                  Secured Party or its assignee. The surrender, upon payment or
                  otherwise, of any Note or any of the other documents
                  evidencing any of the Indebtedness shall not affect the right
                  of Secured Party to retain the Collateral for such other
                  Indebtedness as may then exist or as it may be reasonably
                  contemplated will exist in the future. This Agreement shall
                  automatically be reinstated if Secured Party is ever required
                  to return or restore the payment of all or any portion of the
                  Indebtedness (all as though such payment had never been made).

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<PAGE>

            DEBTOR AGREES THAT SECURED PARTY AND/OR ITS SUCCESSORS AND ASSIGNS
            SHALL HAVE THE OPTION BY WHICH STATE LAWS THIS AGREEMENT SHALL BE
            GOVERNED AND CONSTRUED: (A) THE LAWS OF THE COMMONWEALTH OF
            VIRGINIA; OR (B) IF COLLATERAL HAS BEEN PLEDGED TO SECURE THE
            LIABILITIES, THEN BY THE LAWS OF THE STATE OR STATES WHERE THE
            COLLATERAL IS LOCATED, AT SECURED PARTY'S OPTION. THIS CHOICE OF
            STATE LAWS IS EXCLUSIVE TO THE SECURED PARTY. DEBTOR SHALL NOT HAVE
            ANY OPTION TO CHOOSE THE LAWS BY WHICH THIS AGREEMENT SHALL BE
            GOVERNED. DEBTOR ACKNOWLEDGES THAT THIS AGREEMENT IS BEING SIGNED BY
            THE SECURED PARTY IN PARTIAL CONSIDERATION OF SECURED PARTY'S RIGHT
            TO ENFORCE IN THE JURISDICTION STATED ABOVE. DEBTOR CONSENTS TO
            JURISDICTION IN THE COMMONWEALTH OF VIRGINIA OR THE STATE IN WHICH
            ANY COLLATERAL IS LOCATED AND VENUE IN ANY FEDERAL OR STATE COURT IN
            THE COMMONWEALTH OF VIRGINIA OR THE STATE IN WHICH COLLATERAL IS
            LOCATED FOR SUCH PURPOSES AND WAIVES ANY AND ALL RIGHTS TO CONTEST
            SAID JURISDICTION AND VENUE AND ANY OBJECTION THAT SAID COUNTY IS
            NOT CONVENIENT. DEBTOR WAIVES ANY RIGHTS TO COMMENCE ANY ACTION
            AGAINST SECURED PARTY IN ANY JURISDICTION EXCEPT VIRGINIA, OR IF
            SECURED PARTY CHOOSES TO LITIGATE IN A STATE WHERE COLLATERAL IS
            LOCTAED THEN IN SUCH COUNTY AND STATE.

      IN WITNESS WHEREOF, Debtor and Secured Party, intending to be legally
bound hereby, have duly executed this Agreement in one or more counterparts,
each of which shall be deemed to be an original, as of the day and year first
aforesaid.

SECURED PARTY:                             DEBTOR:

OXFORD FINANCE CORPORATION                 PTC THERAPEUTICS, INC.

By: /S/ MICHAEL J. ALTENBURGER             By: /S/ WILLAIM BAIRD

Name: Michael J. Altenburger               Name: William Baird III

Title: Chief Financial Officer             Title: Vice President Finance

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